drm/i915: Defer final intel_wakeref_put to process context

As we need to acquire a mutex to serialise the final
intel_wakeref_put, we need to ensure that we are in process context at
that time. However, we want to allow operation on the intel_wakeref from
inside timer and other hardirq context, which means that need to defer
that final put to a workqueue.

Inside the final wakeref puts, we are safe to operate in any context, as
we are simply marking up the HW and state tracking for the potential
sleep. It's only the serialisation with the potential sleeping getting
that requires careful wait avoidance. This allows us to retain the
immediate processing as before (we only need to sleep over the same
races as the current mutex_lock).

v2: Add a selftest to ensure we exercise the code while lockdep watches.
v3: That test was extremely loud and complained about many things!
v4: Not a whale!

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111295
References: https://bugs.freedesktop.org/show_bug.cgi?id=111245
References: https://bugs.freedesktop.org/show_bug.cgi?id=111256
Fixes: 18398904ca9e ("drm/i915: Only recover active engines")
Fixes: 51fbd8de87dc ("drm/i915/pmu: Atomically acquire the gt_pm wakeref")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190808202758.10453-1-chris@chris-wilson.co.uk

1 files changed, 19 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
index e8a18d4b27c9..fb39d99cd6ee 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
@@ -17,14 +17,31 @@ enum {
 	INTEL_GT_PARK,
 };
 
-void intel_gt_pm_get(struct intel_gt *gt);
-void intel_gt_pm_put(struct intel_gt *gt);
+static inline bool intel_gt_pm_is_awake(const struct intel_gt *gt)
+{
+	return intel_wakeref_is_active(&gt->wakeref);
+}
+
+static inline void intel_gt_pm_get(struct intel_gt *gt)
+{
+	intel_wakeref_get(&gt->wakeref);
+}
 
 static inline bool intel_gt_pm_get_if_awake(struct intel_gt *gt)
 {
 	return intel_wakeref_get_if_active(&gt->wakeref);
 }
 
+static inline void intel_gt_pm_put(struct intel_gt *gt)
+{
+	intel_wakeref_put(&gt->wakeref);
+}
+
+static inline int intel_gt_pm_wait_for_idle(struct intel_gt *gt)
+{
+	return intel_wakeref_wait_for_idle(&gt->wakeref);
+}
+
 void intel_gt_pm_init_early(struct intel_gt *gt);
 
 void intel_gt_sanitize(struct intel_gt *gt, bool force);